2013-02-07 VIR Measles, Mumps and Slow Viruses

Question 1

Describe the structure of measles and mumps

Answer 1

both measles and mumps are paramyxoviruses:

Has a single piece(-)ssRNA (therefore virion has a viral RDRP and cannot undergo rapid and major antigenic shifts) in helical nucleocapsid with an envelope embedded with H

Question 2

Compare the antigenic relationship of measles and mumps to other classic paramyxoviruses

Answer 2

mumps has a antigenically related to the parainfuenza viruses but measlues isn’t

Question 3

How is mumps spread?

Answer 3

respiratory droplets

Question 4

How is measles spread?

Answer 4

respiratory droplets

Question 5

Comare the infection location, incubation time and immunity length for measles/mumps vs. influenza/parainfluenza

Answer 5

parainflu and flu are local (i.e. non-systemic) infections vs. obligatory viremia in measles and mumps

this means longer incubation time for measles/mumps

and that measles/mumps gives longer (i.e. lifelong immunity)

Question 6

What causes so-called “slow” infections?

Answer 6

1) conventional viruses w/ delayed onset of sx
2) unconventional agents (e.g. prions)

Question 7

Describe the course of a slow viral infection.

Answer 7

Takes years for sx to set in

slow but relentless course to death

Question 8

What are prions?

Answer 8

Infectious proteins that lack any detectable nucleic acid

Question 9

What are prion diseases called, as a class, in humans?

Give us the list of them all.

Answer 9

spongiform encephalopathies

Creutzfel-Jacob Disease (CJD), Variant Creutzfeld-Jacob (vCJD), Kuru, Gerstmann-Straussler-Scheinker Syndrome (GSS) and Fatal Familial Insomnia

Question 10

What is the source of variation in paramyxoviruses? How much does it ∆ w/ time?

Answer 10

unsegmented RNA genomes so no reassortment; only source is mutation though this does happen faster b/c RNA pol doesn’t proof

Therefore paramyxoviruses like measles and mumps are antigenically quite stable (i.e. they don’t change much and the original vaccines we have for them still work)

Question 11

Define pantropic

Answer 11

Measles is considered a “pantropic” infection because it affects nearly all parts of the body

Question 12

Mumps

Family = ?

Epidem = ?

Trans = ?

Incubation = ?

Pathogen w/ s/sx = ?

Dx = ?

Prevention = ?

Tx = ?

Answer 12

Family = paramyxoviridae

Epidem = worldwide, peaks in winter; some reccent epidemics have occured in North America

Trans = saliva—>resp droplets

Incubation = ~3 wks

Pathogenesis, s, sx = virus grows in resp epithel—>local lymph nodes—>viremia—>parotids etc.

most people are symptomic (70%)

prodrome: 1st malaise, anorexia, fever; 2nd uni- or bi-lateral parotiditis—>spreads via saliva; 3rd other encapsulated organs via viremia (e.g. testes = orchitis in 30% of post-pubertal males; meninges causing aseptic meningitis pretty common; ovaries and pancrease less common)

Dx = usu clinical; viral culture from saliva, CSF or urine; PCR also; 4x incr in IgG

Prevention = live attenuated vaccine given twice in childhood

Tx = none

Question 13

Measles

Family = ?

Epidem = ?

Trans = ?

Incubation = ?

Pathogen w/ s/sx = ?

Dx = ?

Prevention = ?

Tx = ?

Answer 13

Family = paramyxovirus

Epidem = highly infectious! humans = sole carriers; most contagious dz known but always antigenically the same! caused dz q3 years (# non-immune incr w/ births breakdown in herd immunity)

Trans = resp drops and also tears and urine

Incubation = 2 weeks from exposure to rash

Pathogen w/ s/sx = resp to resp; growth in epithel, lymph nodes and conjunctiva; 100% attack rate (everyone exposed gets it); 1st) prodrome w/ coryza; 2) koplik’s spots (see photo); 3) pathognomonic maulopapular erythema that starts on head and spreads inferiorly

—causes syncytia; rare giant-cell pneumonia w/o rash chez les personnes sans cell-mediated immunity; show cell-med imm imprt for rash

—suppressed cell-mediated immunity—>2° infections that cane be deadly esp. in resource-limited situations = ANERGY

—Photophobia also common

—1:20 pneumonia; 2° bact. otitis media; acute encephalitis —> neuro def if survived

—1-3:1000 death rate

Dx = usu. clinically; culture, 4x incr [Ab] or PCR also available

Prevention = live, attenuated vaccine

Tx = no antiviral therapy available

Question 14

Progressive Multifocal Leukoencephalopathy (PML)

Family = ?

Epidem = ?

Trans = ?

Incubation = ?

Pathogen w/ s/sx = ?

Dx = ?

Prevention = ?

Tx = ?

Answer 14

WILL BE ON BOARDS

Family = polyomaviridae—>JC virus

Epidem = most common chez les immunodéprimées

Trans = unbiquitous

Incubation = long long time

Pathogen w/ s/sx = immunocompromizaiton causes affects oligodendrocytes causing demyelenation: visual field defects, mental status ∆s, weakness—>blindness, dementia, coma and death =(

Dx = PCR of brain biopsy or CSF

Prevention = don’t get cancer or HIV?

Tx = cidofovir may help, but really no effective tx

Question 15

Subacute Sclerosing Panencephalitis (SSPE)

Family = ?
Epidem = ?

Trans = ?

Incubation = ?

Pathogen w/ s/sx = ?
Dx = ?

Prevention = ?

Tx = ?

Answer 15

Family = Paramyxoviridae—>MEASLES VIRUS
Epidem = kids several years after initial infection

Trans = ?

Incubation = “long incubation time”

Pathogen w/ s/sx = slow cognitive decline, psych disturbances—remissions—>terminal paralysis and blindness

Dx = titer of blood and CSF: VERY HIGH Ig titers; Measles Ag in CSF

Prevention = vaccination? still 1:1,000,000 risk of SSPE w/ vaccination as compared to 1:100,000 w/ actual dz

Tx = none =(

Question 16

Scrapie

Family = ?
Epidem = ?

Trans = ?

Incubation = ?

Pathogen w/ s/sx = ?

Prevention = ?

Answer 16

Sheep prion dz

genetic predisposition (inbred sheep at increased risk)

sheep goes crazy scrapes off all its skin

cannot be prevented with UV sterilzation, alyklating agents or formaldehyde

Question 17

Kuru

Family = ?
Epidem = ?

Trans = ?

Pathogen w/ s/sx = ?

Answer 17

Family = prion dz

epidem = limited to Foré

Trans = ingestion, direct injection into brain of chimps, possibly via open skin?

Pathogen = Kuru is a progressive degenerative disorder of the CNS, especially the cerebellum; similar to Scrapie

Question 18

CJD

Family = ?
Epidem = ?

Trans = ?

Incubation = ?

Pathogen w/ s/sx = ?
Dx = ?

Prevention = ?

Tx = ?

Answer 18

Creutzfeld Jacob Disease

Family = prion dzs
Epidem = most cases in 50-70 y/o’s

Trans = 1) sporadic = most cases (sCJD); 2) genetic predisposition (fCJD familial); 3) iatrgoenic (iCJD) **Not linked to diet—vegetarians and meat-eaters have similar incidence

Incubation = clinically with: brain biopsy showing SE; imaging and EEG; definitely with: antiprion Abs

Pathogen w/ s/sx = dementia w/ behav ∆s/mem loss/confusion and myoclonic jerking
Dx = ?

Prevention = no vaccine

Tx = no tx

Question 19

Variant CJD

Answer 19

2. A spongiform encephalopathy of cows (“mad cow disease”) reached epidemic status in Great Britain as a result of using brains and bone marrow from cows and sheep in the manufacture of bovine food.
3. An outbreak of “atypical human Creuzfeld-Jacob disease” (vCJD) in Great Britain has been linked epidemiologically to eating beef from infected cows. Cows were infected by being fed dead cow brains in their feed. =/

Question 20

Paramyxoviruses

Nucleic acid set-up?

Virion structure?

How does it multiply?

Examples?

Answer 20

NA = single (-)ssRNA

Virion = helical enveloped

REPLICAITON:

1) also uses hemagglutinin to adsorb to cell
2) have only one RNA segment (therefore no antigenic shift) and replicates genome in cytosol, but otherwise similar to influenza/orthomyxoviridae: Virion contains RNA-dependent RNA pol, budding, etc.

EXAMPLES: parainfluenza (Croup), RSV, Measles, mumps

Question 21

Polyomaviridae (Formerly Papovavirus)

Nucleic acid set-up?
Virion structure?

(How does it multiply?)
Examples?

Answer 21

Nucleic acid set-up? circular dsDNA genome

Virion structure? non-enveloped

(How does it multiply?)

Examples? JC virus, BK virus and SV40 virus

Question 22

What is the most common cause of croup?

Answer 22

parainfluenza infection (~75% of cases)